(1) Field of the Invention
The present invention relates to a photoresist stripping composition and, more particularly to, a composition having high photoresist dissolving and stripping force.
(2) Description of the Related Art
A semiconductor integrated circuit in a liquid crystal display panel has very fine structures. Such a fine circuit is generally manufactured by uniformly coating a photoresist on an insulating film of an oxide or a conductive metal film of an aluminum (Al) alloy formed on a substrate, exposing and developing the photoresist to form a certain pattern, and etching the metal film or insulating film by using the patterned photoresist as a mask. Then, the remaining photoresist is stripped to finalize the circuit.
U.S. Pat. No. 5,480,585 and Japanese Laid-open Patent Hei. 5-281753 disclose organic strippers comprising alkanolamine of the structural formula H.sub.3n N((CH.sub.2)mOH).sub.n (where m is 2 or 3, and n is 1, 2 or 3), a sulfone compound or sulfoxide compound and a hydroxy compound of the structural formula C.sub.6 H.sub.6n (OH).sub.n (where n is 1, 2 or 3). Japanese Laid-open Patent Hei 4-124668 discloses a photoresist stripping composition including an 20-90% by weight of organic amine, 0.1-20% by weight of phosphoric ester surfactant, 0.1-20% by weight of 2-butyne-1, 4-diol, and the remainder glycolmonoalkylether and/or aprotic polar solvent.
Japanese Laid-open Patent Hei. 8-87118 discloses a stripping composition comprising 50 to 90% by weight of N-alkylalkanolamine and 10 to 50% by weight of dimethylsulfoxide or N-methyl-2-pyrrolidone. It states that even under hard stripping conditions (for example, at high temperature) the composition including N-alkylalkanolamine and the organic solvents prevents the formation of non-soluble impurities, thus, leaving no residues on the substrate.
Japanese Laid-open Patent Sho. 64-42653 discloses a photoresist stripping composition comprising over 50% by weight of dimethylsulfoxide (more desirably over 70% by weight), 1 to 50% by weight of a solvent selected among diethyleneglycolmonoalkylether, diethyleneglycoldialkylether, .gamma.-butyrolactone and 1,3-dimethyl-2-imidazolidinone, and 0.1-5% by weight of nitrogen-including organic hydroxyl compound such as monoethanolamine. It states that the amount of dimethylsulfoxide less than 50% by weight causes great reduction in stripping force, while the amount of nitrogen-including organic hydroxyl compound solvent over 5% by weight corrodes metal film such as aluminum.
Conventional compositions have been mainly used for a dipping method, where the etched semiconductor integrated circuits or the liquid display panel circuits are immersed or dipped in the stripping compositions to remove the photoresist. Thus, the improvement in the composition are mainly focused on good chemical properties, such as stripping force, non-corrosiveness of metal and safety of humans. However, the conventional stripping compositions are not suitable for a single-wafer treatment method using an air knife process to remove the photoresist. The single-wafer treatment method using an air knife process are more frequently used than the dipping method for stripping the photoresist in fabricating large-size liquid crystal display panel devices, because a relatively small amount of the stripping compositions is required. Therefore, there is a need for a stripping composition suitable for both the single-wafer treatment method and the dipping method.
In addition, the stripping composition should have high stripping force at low and high temperatures, and should not leave photoresist residues or impurities on the substrate. Also, a desirable stripper is one whose total amount and composition ratio should remain intact even when the composition is repeatedly used to remove the photoresist. Depending on the constituents of the composition and the ratio thereof, the stripping composition exhibits greatly different characteristics in their stripping forces, metal corrosion properties, complexities of a rinsing process following the photoresist stripping process, environmental safety, workability and price.